Piston and cylinder construction for reciprocating hydraulic motors



y 1949- g L. E. GODFRIAUX 2,471,484

PISTON AND CYLINDER CONSTRUCTION FOR RECIPROCATING HYDRAULIC MOTORSFiled Sept. 20, 1944 3 Sheets-Sheet 1 FIGJ.

Louis E. Godfrz'dmt INVENTORE' ATTORNEY. Y

May 31, 1949 L. E. GODFRIAUX PISTON AND CYL 2,471,484 INDER CONSTRUCTIONFOR Filed Sept. 20, 1944 REC I PROCAT ING HYDRAULI C MOTORS 3Sheets-Sheet 2 FIG. 3.

MOTOR Louis 2.60 rzaux SUM? 4 ms-rmzu'roa REVERSIHG' VALVE PUMP i INVNTOR.

' ATTORNEY May 31, 1949.

. L. PISTON AND CYLINDER CONSTRUCTION FOR RECIPROCATING HYDRAULIC MOTORSFiled Sept.- 20, 1944 3 Sheets-Sheet 3 A LoubEGad/rz'aux INVENTOR.

ATTORNEY E. GODFRIAUX 2,471,484

Patented May 31, 1949 I PISTON AND CYLINDER CONSTRUCTION FORRECIPROCATING HYDRAULIC MOTORS Louis E. Godi'riaux, Madison, .Wis.,.assignor to Gisholt Machine Gompany,-. Madison, Wis., a corporation ofWisconsin Application September 20, 1944, Serial No. 554,883

3 Claims. (01. 121120) This invention relates to a hydraulic motor ofhigh torque efficiency at low speeds.

The invention has as its principal object the construction of motorsadapted to operate with a substantially constant torque output with anygiven pressure over a very wide range of speeds, as, for instance, fromonlya fraction of a revoluper minute to over a hundred revolutions aminute.-

Another object of the invention is to provide a small compact hydraulicmotor of relatively high torque output.

A more specific object is to provide a multicylinder piston typehydraulic motor employing individual rotary cam members for transformingthe power stroke of each piston into rotary motion.

A further specific object is to provide a rotary cam member capable ofdelivering a substantially constant torque force to the shaft during theworking stroke of its respective piston.

Another object is to reduce the overlap of the torque force ofsuccessive cylinders to obtain a more uniform torque output for themotor.

In carrying out the invention the rotary cam member secured on the motorshaft is designed to be turned or rotated approximately uniformly 'asthe piston moves uniformly in its working stroke, and a suflicientnumber of pistons are employed to engage either the same cam member orsimilar individual cam members to provide a substantially constanttorque force for the motor shaft. The cam members are further designedto provide a nearly constant torque force during the overlap between thesuccessive working strokes of the several pistons when the latter areaccelerating and decelerating.

An embodiment of the invention is illustrated in the accompanyingdrawings in which:

Figure 1 is a longitudinal central section through the motor axially ofits shaft;

Fig. 2 is a transverse section through the motor taken on line 22 ofFig. 1 centrally of one of the cylinders;

Fig. 3 is a schematic illustration of the fluid circuit for the motor;and

Fig. 4 is an enlarged diagrammatic illustration of the method of layingout the cam. v

The motor comprises, in general, a motor shaft i and a plurality ofpower cylinders 2 disposed in a housing 3. A suitable distributor 4 isgeared to the shaft l to be driven in synchronism with the motor forcontrolling the distribution of pressure fluid to the cylinders 2.

The shaft l is mounted to rotate in bearings 5 in housing 3, and toextend from the housing at one end where a worm gear 6 secured upon theshaft drives a suitable-power shaft 1.

r The shaft I has a plurality of cam members 8 integral therewith anddisposed in axially spaced relation correspondingwith the spacing of thecentersof cylinders 2.

Each cylinder 2 has apiston 9 operating therein and carrying a rollerIII which is mounted on suitable bearings at the outer end of thepiston. The roller ID of each piston is adapted to engagethecorresponding cam member 8 and to drive the same during the workingstroke of the piston.

The pistons 9 are driven upwardly in succession by the timed admissionof pressure fluid into the corresponding cylinders 2 through the port IIfor each cylinder. The distributor furnishes and controls the inlet ofpressure fluid to the respective cylinders in order to raise thecorresponding pistons therein successively and provide the power strokesfor the pistons.

Just after the piston 9 for each cylinder reaches its uppermost positionthe supply of pressure fluid beneath the same is cut off by distributor4 and the distributor then exhausts fluid through port H. The piston 9thereupon lowers partially by its own gravity, but more particularly bythe engagement of the back side'of cam member 8 with roller l0 drivingit downwardly.

The cam members 8 are constructed of curved cam contour having a majorand minor axis representing the outer and inner extremity of the pistonmovement, respectively. The shape or contour of the cam in that portionof the movement of the piston representing the power stroke is such thatfor each increment of vertical movement of the piston there will be acorresponding increment of rotation of the'cam and the roller I I! willbe kept'in pressure contact with the cam throughout the movement. Theshape or contour of the cam in the remaining portion of its surface isrelatively unimportant, although it is preferable to provide a similarcurve on the back side of the cam so that the motor can be reversed indirection of operation.

In designing the cam 8, the curvature is laid out by taking determinedincrements-of movement of roller l0 along the radius of shaft I, andplotting the surface of the cam for corresponding increments of rotationof the shaft, the surface of the cam being located at the point ofcontact of the roller l0 so that the latter will always be in contactwith the cam during the working stroke.

A specific method of laying out one quadrant ofthe cam 8 is illustratedin Fig.4 in which line A-A is the longitudinal center line for the camand line B-B is the transverse center line at right angles to line A-A.C is the center of the cam and is located at the intersection of linesA-A and B-B. The ends of the cam are first drawn as short arcs with C asthe center and with a radius equal to one-half the proposed length ofthe cam.

LineC-D is then drawn at an angle of 10 to line A-A and point E islocated on the line at the center of the roller it when the latter rideson the end of the cam at itsmaximum distance from C.

Line C-F is then drawn at an angle of 60 to line -D and point G islocated on'the line at the center of the roller l0 when the latter is atits minimum distance from point C in the operation of the motor, asdetermined by the layout of the working stroke for the piston 9.

The point E is transposed to line C-F and the distance E-G is thendivided into six equal spaces to provide intermediate points H, I, J, Kand L, reading outwardly from point G.

The 60 angle between 0-1) and C-F is divided into six equal angles ofeach to provide intermediate lines C-M, C-N, C-O, C-P and C-Q, readingfrom line CF toward C-D.

Point H on line 0-1 is then transposed to the adjacent line C-M; point Iis transposed to the next line C-N; point J is transposed to line C-0;point K is transposed to line 0-1; and point L is transposed to line CQ.These points represent respective locations for the center of roller H)as the latter rides along the cam.

The several locations for roller III are then outlined with the originalpoints E and G and the transposed points H, I, J, K and L as centers.

The curve of the cam 8 representing the working stroke is then drawntangent to the roller at the several positions referred to to constitutethe cam surface Rr-S- R is the point at which the cam surface intersectsthe end are of the cam. S is the point of the working cam surfacenearest 0.

A central curve S-S is drawn to connect the working cam surfaces of twoadjacent quadrants of cam 8. The end arcs R-R represent idling arcs whenthe piston 9 is retracted to the lower end of its cylinder while thearcs S-S represent the idling arcs when the piston 9 is extended fromits cylinder and at the top of its stroke.

The curves R,-S in alternate quadrants of the cam 8 represent theworking cam surfaces for the motor by which the cam is driven by piston9, and those in the intermediate quadrants represent the cam surfacesfor the return strokes of the piston. Each cam surface R-S is active fora little over 60 of rotation of the cam 8 and since there are threecylinders, each having two working strokes per revolution of the cam, asubstantially constant torque is provided for the entire 360 ofrevolution of the cam. The slight amount of overlap provided by themovement of roller in when its center approaches point E is suflicientto join the power strokes of successive pistons. When the center ofroller l0 leaves point G the curve S-S preferably causes the roller tostop in its inward movement except for a slight overla in transmittingthe torque load to the next active piston 9.

Two working strokes of the piston III are obtained for each revolutionof the cam by providing the latter with two diametricaly opposite camprojections of major axis, as shown in Fig. 2.

The curve of the cam 8 in the region of contact of roller l0 during theworking stroke of the piston produces a constant torque or turningmoment on shaft 1 when a constant pressure of oil is applied to thepiston 9. The speed of movement or of rotation of shaft I is dependentupon the volume of oil supplied to the cylinder in a given time.

In order to apply a constant torque to shaft I, the three cylinders havetheir corresponding cams ofiset circurnferentially on shaft 1 so thateach working stroke of a piston drives the shaft through slightly morethan one-sixth of a revolution and the several pistons operate insuccession ,sion of power strokes necessary in driving the shaft. Thesequence of admission and exhaust of oil from the respective cylindersshould correspond with the positioning of the respective cams to providethe required succesto apply a continuous torque to the shaft. It ispossible to provide a larger number of cylinders, each corresponding toa smaller portion of the rotation of the shaft. Where two cylindersonly, are employed there is some difllculty in obtaining sufficientoverlap to have a constant torque forthe motor.

Three cylinders have been found to be most satisfactory since with thatnumber it is possible to provide eificient cams for transforming theradial movement of the pistons into rotary movement of the shaft with aminimum of overlap between successive pistons. The actual overlap may beconsiderably less than 15% of the total cycle of movement and iscontrolled by the cam contour to provide a cumulative effect duringoverlap approximately equal to the desired constant torque value.

While the cylinders have been described as being disposed side by sidein parallel relationship in a common plane, it is possible to arrangethem in other relationships wherein they act upon one or more cammembers to apply the desired torque to the motor shaft. However, forcompactness of structure, it is preferred to mount the cylinders in anaxial plane as shown, wherein each piston engages a separate cam member.

There is a key l2 extending through each cylinder wall and into alongitudinal slot l3 in the corresponding piston 9 to prevent rotationof the pistons on their respective axes, so that the rollers Ill aremaintained parallel to the shaft l.

Each of the cylinders 2 is of substantial length and the correspondingpistons 9 are long to provide for a substantial bearing surfacebetweenthe pistons and the cylinder walls and preventwear from side thrust ofthe cams 8 against the rollers Ill. The pistons 9 are tubular at theirinner ends and telescope over a central tubular plug [4 secured to theend of the cylinder around the corresponding port II. The movement ofthe piston downwardly during the exhaust stroke effects a rapid flow ofthe liquid over the upper edge of plug l4 and down therethrough to portI l and tends to drive out any gas bubbles that may have formed in thecylinder.

Referring to Fig. 3, the distributor 4 has a connecting passage l5leading to each port II. An inlet pipe l6 supplies power fluid to thedistributor 4, and an exhaust pipe l1 receives exhaust fluid from thedistributor 4. In operation the motor may be reversed by valve means l8for reversing the connections to pipes l 6 and 11 so that pipe ll may beutilized to supply power fluid to distributors 4 and pipe l6 utilized toexhaust fluid from distributor 4. This reversal of operation of thehaving a port therein for the admission and exhaust of pressure liquidfor the cylinder, a piston disposed in said cylinder, a cylindricalskirt for said piston extending from the piston crown toward said headand of substantial thickness to provide for a reasonably tight fit ofthe skirt with the cylinder walls without binding under the infiuence ofthe liquid pressures on the inside of the skirt, and a tubularscavenging plug extending from said head into said piston to provide ascavenging passage between the plug and piston skirt during movement ofthe piston toward the head, the free end of said plug extending to aposition close to the crown of the piston when the latter has moved toits nearest position, the passage in said plug opening toward saidpiston crown and communicating with said port to supply power liquid tosaid cylinder and exhaust liquid therefrom, and the flow of liquid beingdisplaced by the thick end of the piston skirt through said scavengingpassage providing a scavenging action upon the inside of said piston andefiecting removal of any entrapped air bubbles during exhaust of theliquid from the cylinder through the passage in said plug.

' 2. In a hydraulic motor of the class described, a cylinder disposedwith its axis vertical, a head at the lower end of said cylinder havinga port axially of the cylinder for the admission and exhaust of pressureliquid for the cylinder, a piston disposed in said cylinder, acylindrical skirt for said piston extending downwardly from the pistoncrown toward said head and of substantial thickness to provide for areasonably tight fit of the skirt with the cylinder walls withoutbinding under the influence of the liquid pressures on the inside of theskirt. and a tubular scavenging plug extending upwardly from said headaxially of the cylinder into said piston to provide an annularscavenging passage between the plug and piston skirt during downwardmovement of the piston, the upper end of said plug terminating close tothe piston crown when the latter is in its extreme lower position, thepassage in said tubular plug opening axially upward toward the pistoncrown and communicating with said port to supply power liquid to saidcylinder and exhaust liquid therefrom, and the flow of liquid beingdisplaced by the thick end of the piston skirt through said scavengingpassage providing a scavenging action upon the inside of said pistoncrown and effecting removal of any entrapped air bubbles during exhaustof the liquid-from the cylinder through the passage in said plug.

3. In a fluid motor of the class described, a vertically disposedcylinder of substantial length, a head at the lower end of saidcylinder, 2. piston near the top of said cylinder and closing the same,a central tube extending upward from said head through which motiveliquid is supplied to and exhausted from said cylinder near the topthereof, a piston skirt extending downward from the crown of said pistonbetween the tube and cylinder wall and of a thickness to provide asubstantial displacement of liquid at the lower end of the cylinderduring the downward stroke of,

said piston, and to provide an, annular passage around said tube for thepassage of said displaced liquid upwardly against the piston crown toscavenge air bubbles which may collect in theupper end of the cylinderand fiow the same outwardly LOUIS E. GODFRIAUX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS through said tube.

Number Name Date 423,515 Colborne Mar. 18,- 1890 603,173 Clay Apr. 26,1898 871,634 Rothchild Nov. 19, 1907 1,039,448 Schwarz Sept. 24, 19121,206,387 Sundh Nov. 28, 1916 1,309,257 Martens July 8, 1919 1,414,495Bangs May 2, 1922 1,531,748 Johnson Mar. 31, 1925 1,653,960 Halstead etal Dec. 27, 1927 1,667,213 Marchetti Apr. 24, 1928 1,711,260 CaminezApr. 30, 1929 1,774,087 Dunn Aug, 26, 1930 1,775,108 Omo Sept. 9, 19301,781,416 Sundstrand Nov. 11, 1930 1,873,396 Hallenbeck Aug. 23, 19321,890,244 Barrett et al 1 Dec. 6, 1932 1,938,772 Ernst et a1 Dec. 12,1933 2,081,760 Nardone May 25, 1937 2,086,835 Adkisson et al. July 13,1937 2,107,456 Trapp Feb. 8, 1938 2,304,903 Eppens Dec. 15, 19422,316,408 Dawson Apr. 13, 1943 FOREIGN PATENTS Number Country Date 2,625Great Britain May 25, 1910 529,508 Germany L. July 21, 1931

